This invention relates to the field of high force cable retraction means. Present devices generally utilize spool winding methods. These are limited in the amount of cable that can be retracted (only until the spool is full). Spool winding is also limited in maximum retraction force due to cable damage. The high force retraction causes excessive cable stress from bending and squeezing between the windings on the spool.
Rotating sheaves such as used for elevators cannot provide high force retraction. Elevators overcome this deficiency with counterweights and by utilizing multiple cables.
This invention further relates to a continuous cable pulling device (no limit on pulling length.) U.S. Pat. No. 4,256,199 granted to Sellards shows a serpentine device. This device is limited due to the high bending strains imposed on the cable. U.S. Pat. No. 5,009,353 granted to Alquist shows a continuous loop friction device. This device cannot provide a high normal force needed to achieve high pulling force. U.S. Pat. No. 4,456,226 granted to Stumpmeier shows a piston operated device to provide step action cable retraction. This intermittent motion limits the speed of the traction device and imparts repetitive accelerations on the cable. U.S. Pat. No. 5,082,248 granted to Harig shows a grooved bull wheel device with a continuous looping pressure chain. This apparatus provides continuous cable pulling. With additional pressure chains, the apparatus would also be capable of high pulling force. The disadvantages remaining would include the 360 degree cable bending arc, complexity, risk of the cable coming out of the bull wheel groove, and difficulty in threading cable through the apparatus.
The present invention further relates to gondola movement on a cable. The cable traction apparatus would be the motive force to cause movement of the gondola along the cable. In this configuration, the traction apparatus is affixed to the gondola and the cable is stationary.